EP0816558B1 - Process for increasing the degree of whiteness of paper making stock from recycled paper - Google Patents

Process for increasing the degree of whiteness of paper making stock from recycled paper Download PDF

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Publication number
EP0816558B1
EP0816558B1 EP97108991A EP97108991A EP0816558B1 EP 0816558 B1 EP0816558 B1 EP 0816558B1 EP 97108991 A EP97108991 A EP 97108991A EP 97108991 A EP97108991 A EP 97108991A EP 0816558 B1 EP0816558 B1 EP 0816558B1
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EP
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Prior art keywords
bleaching
bleaching process
paper
during
whiteness
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
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EP97108991A
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German (de)
French (fr)
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EP0816558A1 (en
Inventor
Volker Dr. Gehr
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Voith Paper Fiber and Environmental Solutions GmbH and Co KG
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Voith Sulzer Stoffaufbereitung GmbH
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    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
    • D21C9/10—Bleaching ; Apparatus therefor
    • D21C9/147—Bleaching ; Apparatus therefor with oxygen or its allotropic modifications
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
    • D21C9/10—Bleaching ; Apparatus therefor
    • D21C9/16—Bleaching ; Apparatus therefor with per compounds
    • D21C9/163—Bleaching ; Apparatus therefor with per compounds with peroxides

Definitions

  • the invention relates to a method for increasing the whiteness of Waste paper obtained paper fibers according to the preamble of claim 1.
  • DE-A-19 54 267 describes a method for delignifying cellulose-containing material, in which pulp is to be produced by breaking down and dissolving out lignin.
  • a delignification step with an alkaline extraction is proposed, the effect of which is improved by O 2 or air.
  • a Mg compound is added which protects the carbohydrates, ie the cellulose, from chain degradation and thereby prevents the strength of the cellulose produced from being lost.
  • a significant increase in the degree of whiteness cannot be achieved with this method, at best a preparation for a subsequent whiteness-increasing bleach.
  • Bleaching and delignification are different chemical processes with different effects and parameters, even if the term "bleaching" is sometimes used for delignification in somewhat sloppy usage.
  • the subclaims describe particularly advantageous embodiments of the Procedure. Different directions can be followed. As you know, change the flow properties of the fiber material are in the material density range above 5% considerable, depending on how the consistency is chosen for the machining process. Here, e.g. the range between approx. 5 and 12% often as the medium density range and which is referred to as high density or high consistency. There are some indications that the medium density range for the process according to the invention brings special advantages, since the flow properties are still relatively good, although already a high mass concentration in the bleaching vessel is possible. With a bleaching vessel Reactor meant in which the pressurized pulp with the Bleaching chemicals and the above Gas mixture reacts.
  • the residence time in which the bleaching process takes place also has an effect on the effect of the Procedure.
  • the exact time at which the process runs optimally depends on of course, depending on a variety of boundary conditions. It is often also a economical compromise, since long dwell times improve the effect can, but also require large reaction vessels.
  • Waste paper P is suspended in hot water W and, at a consistency of approx. 12%, mixed with chemicals CH in a mixer 1, that is 1% peroxide, 1% NaOH and other auxiliary chemicals.
  • the suspension is then conveyed into the pressurized reaction vessel 3 using a medium density pump 2. If the chemicals CH ′ are added immediately before the medium density pump 2, this can also function as a mixing pump.
  • the reaction vessel 3, in which the material can remain for about 15 minutes, is designed as a downward-flowing reaction tower.
  • Heated room air A is blown into this vessel at 80 ° Celsius with a pressure of 1.4 bar absolute by a blower 4, in such an amount that this pressure is maintained even within the reaction tower.
  • the fiber material treated in this way passes through a blow-out opening 5 into a collecting vessel 6, where it is diluted with water W '.
  • the system diagram only shows the actual bleaching section.
  • Raw material and requirements are a number of further process steps before and then necessary, e.g. around printed and / or colored waste paper to a white Process quality.
  • contaminants have to be removed cannot or should not be bleached.

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  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Wood Science & Technology (AREA)
  • Paper (AREA)

Abstract

The whiteness of paper fibre, in an aqueous suspension containing at least 5% dry material, is increased by the use of oxidising bleaches, the bleaching action being further increased by molecular O2. The process takes place under excess pressure of at least 0.1 bar and the gas used contains 50% O2 at the most.

Description

Die Erfindung bezieht sich auf ein Verfahren zur Erhöhung des Weißgrades von aus Altpapier gewonnenen Papierfasern gemäß dem Oberbegriff des Anspruchs 1.The invention relates to a method for increasing the whiteness of Waste paper obtained paper fibers according to the preamble of claim 1.

Ein ähnliches Verfahren ist z.B. aus der EP-A-0 557 651 bekannt, das ebenfalls bei der Aufbereitung von gemischtem Altpapier Anwendung findet. Altpapier wird eingedickt und bei erhöhter Temperatur mit molekularem Sauerstoff und Peroxid behandelt. Dadurch werden die an sich bekannten chemischen Umsetzungen veranlaßt, bei denen insbesondere das Lignin von den Fasern gelöst wird. Nach dem Ausblasen aus dem Druckraum wird dann der gebleichte Stoff gewaschen. Das in Lösung gebrachte Lignin wird mit dem Waschwasser entfemt. Mit Hilfe eines solchen Verfahrens soll und kann der Weißgrad des Papierstoffes gesteigert werden, d.h., daß das später daraus erzeugte Papier möglichst weiß sein soll.A similar procedure is e.g. known from EP-A-0 557 651, which also in the Processing of mixed waste paper is used. Waste paper is thickened and treated with molecular oxygen and peroxide at elevated temperature. This causes the chemical reactions known per se, in which especially the lignin is released from the fibers. After blowing out of the The bleached fabric is then washed in the pressure chamber. The lignin brought into solution is removed with the wash water. With the help of such a procedure, it should and can the degree of whiteness of the paper stock is increased, i.e. that which is later produced from it Paper should be as white as possible.

Aus einer anderen Patentschrift, der US-A- 5,211,809, ist ein Altpapierbleichverfahren bekannt, bei dem ebenfalls elementarer Sauerstoff eingesetzt wird. Das Verfahren arbeitet jedoch ausschließlich mit intensiver chemischer Einwirkung auf den Stoff, und zwar einer gezielt herbeigeführten chemischen Reaktion zwischen den enthaltenen Farbstoffen und dem Sauerstoff. Das heißt, daß es sich hier um eine Entfernung bzw. Reduzierung von Farbstoffen handelt.From another patent, US-A-5,211,809, is a waste paper bleaching process known in which elemental oxygen is also used. The procedure works only with an intensive chemical influence on the material, and a specifically induced chemical reaction between the contained Dyes and oxygen. This means that this is a distance or Reduction of dyes.

In der DE-A- 19 54 267 wird ein Verfahren zur Delignifizierung von zellulosehaltigem Material beschrieben, bei dem durch Abbau und Herauslösen von Lignin Zellstoff hergestellt werden soll. Dazu wird eine Delignifizierungsstufe mit einer alkalischen Extraktion vorgeschlagen, deren Wirkung durch O2 oder Luft verbessert wird. Weiterhin wird eine Mg-Verbindung zugegeben, die die Kohlenhydrate, also die Zellulose vor dem Kettenabbau schützt und dadurch Festigkeitseinbußen des erzeugten Zellstoffes verhindert. Ein signifikanter Weißgradanstieg ist durch dieses Verfahren nicht erzielbar, allenfalls eine Vorbereitung für eine nachfolgende weißgraderhöhende Bleiche. Bleichen und Delignifizieren sind unterschiedliche chemische Prozesse mit unterschiedlichen Wirkungen und Parametern, auch wenn bei etwas nachlässigem Sprachgebrauch der Begriff "Bleichen" gelegentlich für Delignifizieren verwendet wird.DE-A-19 54 267 describes a method for delignifying cellulose-containing material, in which pulp is to be produced by breaking down and dissolving out lignin. For this purpose, a delignification step with an alkaline extraction is proposed, the effect of which is improved by O 2 or air. Furthermore, a Mg compound is added which protects the carbohydrates, ie the cellulose, from chain degradation and thereby prevents the strength of the cellulose produced from being lost. A significant increase in the degree of whiteness cannot be achieved with this method, at best a preparation for a subsequent whiteness-increasing bleach. Bleaching and delignification are different chemical processes with different effects and parameters, even if the term "bleaching" is sometimes used for delignification in somewhat sloppy usage.

Es ist Aufgabe der Erfindung, ein Verfahren zu schaffen, mit dem der Weißgrad mit relativ geringem Aufwand gesteigert werden kann. Dabei soll sowohl die Aufbereitung von bedrucktem, gemischten Altpapier zu weißem und melierungsfreien Papier verbessert werden können. Die Betriebssicherheit soll möglichst hoch sein.It is an object of the invention to provide a method with which the degree of whiteness can be increased relatively little effort. Both the preparation and from printed, mixed waste paper to white and mottling-free paper can be improved. The operational security should be as high as possible.

Diese Aufgabe wird durch die im Kennzeichen des Anspruchs 1 genannten Maßnahmen gelöst.This object is achieved by the measures mentioned in the characterizing part of claim 1 solved.

Weil zum Bleichen kein reiner gasförmiger Sauerstoff benötigt wird und die Kosten für den Sauerstoff praktisch entfallen, kann das Verfahren erheblich verbilligt werden. Ein Gasgemisch von Inertgas und Sauerstoff - wie z.B. Luft - unter erhöhtem Druck kann die gestellte Aufgabe gut lösen und erlaubt eine besonders wirtschaftliche Verfahrensweise. Es ist lediglich ein Kompressor für die Komprimierung der Luft erforderlich. Vorteilhaft ist auch, daß der Papierfaserstoff zumeist schon Luft enthält, die bei der Bleichreaktion zur Verfügung steht. Neben den deutlich geringeren Kosten ist bei der Verwendung eines solchen Gasgemisches auch die Explosionsgefahr geringer als mit reinem Sauerstoff. Gerade dieser letztgenannte Vorteil kann bei Altpapieranlagen mit dem bekanntlich rauhen Betrieb, der vom Umgang mit dem heterogenen Rohstoff geprägt wird, von großem Nutzen sein.Because no pure gaseous oxygen is required for bleaching and the costs for the oxygen is practically eliminated, the process can be made considerably cheaper. On Gas mixture of inert gas and oxygen - such as Air - under increased pressure solve the task well and allows a particularly economical procedure. All that is required is a compressor to compress the air. It is also advantageous that the paper pulp mostly already contains air that is in the Bleaching reaction is available. In addition to the significantly lower costs, the Using such a gas mixture also reduces the risk of explosion than with pure oxygen. It is precisely this latter advantage that can be used in waste paper systems the well-known rough company, which is shaped by the handling of the heterogeneous raw material will be of great benefit.

Die Unteransprüche beschreiben besonders vorteilhafte Ausführungsformen des Verfahrens. Dabei können verschiedene Richtungen verfolgt werden. Bekanntlich ändern sich in dem Stoffdichtebereich oberhalb von 5 % die Fließeigenschaften des Faserstoffs beträchtlich, je nach dem wie die Stoffdichte für den Bearbeitungsprozeß gewählt wird. Dabei wird z.B. der Bereich zwischen ca. 5 und 12 % oft als Mittelstoffdichtebereich und der darüber als Hochstoffdichte oder Hochkonsistenzbereich bezeichnet. Es gibt einige Hinweise, daß der Mittelstoffdichtebereich für das erfindungsgemäße Verfahren besondere Vorteile bringt, da die Fließeigenschaften noch relativ gut sind, wobei bereits eine hohe Massenkonzentration im Bleichgefäß möglich ist. Mit Bleichgefäß ist der Reaktor gemeint, in dem der unter Druck stehende Faserstoff mit den Bleich-Chemikalien und dem o.g. Gasgemisch reagiert.The subclaims describe particularly advantageous embodiments of the Procedure. Different directions can be followed. As you know, change the flow properties of the fiber material are in the material density range above 5% considerable, depending on how the consistency is chosen for the machining process. Here, e.g. the range between approx. 5 and 12% often as the medium density range and which is referred to as high density or high consistency. There are some indications that the medium density range for the process according to the invention brings special advantages, since the flow properties are still relatively good, although already a high mass concentration in the bleaching vessel is possible. With a bleaching vessel Reactor meant in which the pressurized pulp with the Bleaching chemicals and the above Gas mixture reacts.

Auch die Verweilzeit, in der der Bleichvorgang abläuft, hat Einfluß auf den Effekt des Verfahrens. Bei welcher konkreten Zeit das Verfahren optimal abläuft, hängt selbstverständlich von einer Vielzahl von Randbedingungen ab. Oft ist es auch ein wirtschaftlicher Kompromiß, da lange Verweilzeiten zwar den Effekt verbessern können, aber auch große Reaktionsgefäße erfordern.The residence time in which the bleaching process takes place also has an effect on the effect of the Procedure. The exact time at which the process runs optimally depends on of course, depending on a variety of boundary conditions. It is often also a economical compromise, since long dwell times improve the effect can, but also require large reaction vessels.

Die Erfindung wird erläutert anhand einer Zeichnung, die eine einfache Anlage zur Durchführung des Verfahrens schematisch darstellt. Dieses Schema und die Versuchsparameter, nach denen das Verfahren sehr gut und effektiv durchgeführt werden kann, werden im folgenden beispielhaft erklärt:
Altpapier P wird in heißem Wasser W suspendiert und bei einer Stoffdichte von ca. 12 % in einem Mischgerät 1 mit Chemikalien CH, das sind hier 1 % Peroxid, 1 % NaOH und weitere Hilfschemikalien, vermischt. Anschließend wird die Suspension mit einer Mittelstoffdichtepumpe 2 in das unter Druck stehende Reaktionsgefäß 3 gefördert. Werden die Chemikalien CH'unmittelbar vor der Mittelstoffdichtepumpe 2 zugegeben, kann diese auch als Mischpumpe fungieren. Das Reaktionsgefäß 3, in dem der Stoff etwa 15 Minuten verweilen kann, ist als abwärts durchflossener Reaktionsturm ausgeführt. In dieses Gefäß wird erhitzte Raumluft A bei 80° Celsius mit einem Druck von 1,4 bar absolut durch ein Gebläse 4 eingeblasen, und zwar in einer solchen Menge, daß auch innerhalb des Reaktionsturms dieser Druck aufrechterhalten wird. Durch eine Ausblasöffnung 5 gelangt der so behandelte Faserstoff nach der bereits erwähnten Verweilzeit von ca. 15 Minuten in ein Auffanggefäß 6, wobei er mit Wasser W' verdünnt wird.The invention is explained with reference to a drawing which schematically represents a simple system for carrying out the method. This scheme and the test parameters according to which the method can be carried out very well and effectively are explained in the following by way of example:
Waste paper P is suspended in hot water W and, at a consistency of approx. 12%, mixed with chemicals CH in a mixer 1, that is 1% peroxide, 1% NaOH and other auxiliary chemicals. The suspension is then conveyed into the pressurized reaction vessel 3 using a medium density pump 2. If the chemicals CH ′ are added immediately before the medium density pump 2, this can also function as a mixing pump. The reaction vessel 3, in which the material can remain for about 15 minutes, is designed as a downward-flowing reaction tower. Heated room air A is blown into this vessel at 80 ° Celsius with a pressure of 1.4 bar absolute by a blower 4, in such an amount that this pressure is maintained even within the reaction tower. After a residence time of about 15 minutes, the fiber material treated in this way passes through a blow-out opening 5 into a collecting vessel 6, where it is diluted with water W '.

Das Anlagenschema zeigt nur den eigentlichen Bleichabschnitt. Je nach eingesetztem Rohstoff und Anforderungen ist eine Vielzahl von weiteren Verfahrensschritten davor und danach notwendig, z.B. um bedrucktes und/oder gefärbtes Altpapier zu einer weißen Qualität aufzubereiten. Zudem müssen in vielen Fällen Störstoffe entfernt werden, die nicht gebleicht werden können oder sollen.The system diagram only shows the actual bleaching section. Depending on the used Raw material and requirements are a number of further process steps before and then necessary, e.g. around printed and / or colored waste paper to a white Process quality. In addition, in many cases, contaminants have to be removed cannot or should not be bleached.

Selbstverständlich ist bei der Vielzahl möglicher Anwendungsfälle und unterschiedlicher ökonomischen Betrachtungen auch eine andere Ausgestaltung des Bleichverfahrens selbst denkbar. Dabei kann die allgemein bekannte Tatsache eine Rolle spielen, daß erhöhte Temperaturen den chemischen Effekt beträchtlich beschleunigen. Ähnliches gilt für den Druck, da sich dadurch der Partialdruck des Gasgemisches und des darin befindlichen Sauerstoffes und somit das Angebot an Sauerstoff-Molekülen erhöhen läßt. Im allgemeinen kann auch eine angehobene Alkalität, etwa pH 12 und mehr, den Effekt positiv beeinflussen, wobei allerdings auch berücksichtigt werden muß, daß einige Papierfasern durch zu hohe Alkalität vergilben können.Of course, with the multitude of possible applications and different economic considerations also a different configuration of the Bleaching process itself conceivable. The well-known fact can play a role in this play that elevated temperatures accelerate the chemical effect considerably. The same applies to the pressure, since this changes the partial pressure of the gas mixture and the contained oxygen and thus increase the supply of oxygen molecules leaves. Generally, increased alkalinity, such as pH 12 and above, can also be used Influence the effect positively, although it must also be taken into account that some paper fibers can yellow due to high alkalinity.

Wird der Bleichprozeß bei einem Trockengehalt über 15 % durchgeführt, muß in der Regel eine davorliegende Eindickstufe verwendet werden.If the bleaching process is carried out with a dry content above 15%, the As a rule, a previous thickening stage should be used.

Claims (12)

  1. A method of increasing the whiteness of paper pulp (P) obtained from waste paper and in the form of an aqueous suspension with at least 5 % solids content using oxidising bleaching chemicals (CH, CH'), in which the bleaching action is further increased by molecular oxygen and the bleaching process takes place at an overpressure of at least 0.1 bar,
    characterised in that
    the molecular oxygen originates from a gas (A), at most 50 % of which consists of oxygen.
  2. A method according to claim 1,
    characterised in that
    the gas (A) is air.
  3. A method according to claim 1 or 2,
    characterised in that
    the gas (A) is supplied to the paper pulp.
  4. A method according to claim 3,
    characterised in that
    the overpressure is generated during the bleaching process by supplying the gas (A).
  5. A method according to claim 1, 2, 3 or 4,
    characterised in that
    the bleaching chemicals (CH, CH') contain peroxide.
  6. A method according to claim 1, 2, 3, 4 or 5,
    characterised in that
    the bleaching period, during which the paper pulp (P) is under overpressure, amounts to at least 10 minutes.
  7. A method according to claim 1, 2, 3, 4, 5 or 6,
    characterised in that
    the absolute pressure of the bleaching process amounts to at least 1.5 bar.
  8. A method according to any one of the preceding claims,
    characterised in that
    the paper pulp (P) exhibits a solids content of between 5 and 12 % during the bleaching process.
  9. A method according to claim 1, 2, 3, 4, 5, 6 or 7,
    characterised in that
    the paper pulp (P) exhibits a solids content of between 12 and 40 % during the bleaching process.
  10. A method according to any one of the preceding claims,
    characterised in that
    the temperature amounts to more than 60° Celsius during the bleaching process.
  11. A method according to claim 10,
    characterised in that
    the temperature amounts to more than 100° Celsius during the bleaching process.
  12. A method according to any one of the preceding claims,
    characterised in that
    the environment is at least pH = 10 during the bleaching process.
EP97108991A 1996-06-29 1997-06-04 Process for increasing the degree of whiteness of paper making stock from recycled paper Expired - Lifetime EP0816558B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE19626200 1996-06-29
DE19626200A DE19626200C2 (en) 1996-06-29 1996-06-29 Process for increasing the whiteness of waste paper pulp

Publications (2)

Publication Number Publication Date
EP0816558A1 EP0816558A1 (en) 1998-01-07
EP0816558B1 true EP0816558B1 (en) 2001-12-05

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EP97108991A Expired - Lifetime EP0816558B1 (en) 1996-06-29 1997-06-04 Process for increasing the degree of whiteness of paper making stock from recycled paper

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EP (1) EP0816558B1 (en)
AT (1) ATE210217T1 (en)
CA (1) CA2208940A1 (en)
DE (1) DE19626200C2 (en)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE19751173A1 (en) * 1997-11-19 1999-05-27 Voith Sulzer Papiertech Patent Pulp bleaching method especially for recycling used paper materials

Family Cites Families (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA918978A (en) * 1970-01-08 1973-01-16 G. Jamieson Allan Oxygen bleaching
JPS5212801B2 (en) * 1973-02-07 1977-04-09
JPS517203A (en) * 1974-07-10 1976-01-21 Sadayoshi Watanabe Arukariekifurikakeo tokuchotosuru kapponkashokubutsuparupuno sansosankaseizoho
FR2566015B1 (en) * 1984-06-15 1986-08-29 Centre Tech Ind Papier PROCESS FOR BLEACHING MECHANICAL PASTE WITH HYDROGEN PEROXIDE
JPH0364589A (en) * 1989-07-28 1991-03-19 Mitsubishi Gas Chem Co Inc Bleaching of chemical pulp
US5211809A (en) * 1991-05-21 1993-05-18 Air Products And Chemicals, Inc,. Dye removal in oxygen color stripping of secondary fibers
CA2082557C (en) * 1992-02-24 1997-03-11 Charles W. Hankins Integrated pulping process of waste paper yielding tissue-grade paper fibers

Also Published As

Publication number Publication date
DE19626200A1 (en) 1997-05-15
ATE210217T1 (en) 2001-12-15
DE19626200C2 (en) 2001-02-01
CA2208940A1 (en) 1997-12-29
EP0816558A1 (en) 1998-01-07

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